Method and apparatus for producing machine-tool-controlling magnetic tapes directly from drawings



W. H. FENGLER MAGNETIC TAPES DIRECTLY FROM DRAWINGS Filed Jan. 29, 1964 INVEN TOR. ml! 6! Ft/YllK.

ITTOKAIEm United States Patent METHOD AND APPARATUS FOR PRGDUCING MACHINE TOOL CONTROLLING MAGNETIC TAPES DIRECTLY FROM DRAWINGS Werner H. Fengler, 2.3651 Fordson Drive, Dearborn, Mich. Filed Jan. 29, 1964, Ser. No. 340,983 Claims. (Cl. 34633) This invention relates to tape-controlled machine tools and, in particular, to apparatus and methods of producing the magnetic tapes which control the motions of such machine tools.

Hitherto, tape-controlled machine tools have been operated from perforated tapes or from magnetic tapes tran forming the impulses recorded on such tape into feeding motions of the machine tool. Certain prior control sys terns for such machine tools have required the use of computers which interpolate the information prepared on punch cards into magnetic tape-recorded information which is again translated back to punched cards or tape which in turn is fed into the machine tool to precisely control the feeding motion of the cutting tool for a continuous path contouring cut. The present invention eliminates the need for the preparation of punch cards and dispenses with the use of computers for interpolation by sensing and converting the dimensions and directions of lines on working drawings of the part to be produced into three-dimensional feeding impulses recorded on a multi-channel magnetic tape which is then fed into the respectively measured from the intersection of the coordinates representing a starting, Zero or reference position into impulses recorded in the channels of the tape, the tape thus produced being fed into a machine tool where the impulses on the tape are communicated to the cutting tool of the machine as corresponding intervals through which the tool is moved from a reference starting position or origin in directions corresponding to the coordinates of the tape-producing apparatus.

Another object is to provide a method of the foregoing character wherein the three-dimensional characteristics of the front, side and end elevational views and the top plan view of the part or article are translated into the X, Y and Z coordinates of points traveling along instantantaneously corresponding portions of the several views, the impulses corresponding to the position of each point being recorded in different channels of the tape corresponding to the different coordinates, the tape when fed into the machine tool feeding the machine tool by intervals corresponding to the impulses in the several channels of the tape so that the tip of the cutting tool is constantly and continuously positioned at a location on the workpiece corresponding to the X, Y and Z coordinates, in three-dimensional space, of the corresponding points moving along the several views of the drawing, in the plane of the drawing.

Another object is to provide a method as set forth in the object immediately preceding, wherein the sensing device which follows the line of the particular drawing aiso measures and records on another channel of the tape and angle which a radius to the instantaneous curvature of the surface makes with a reference line, the in- 3,178,717 Patented Apr. 13, 1965 ice formation on the tape being translated in the machine tool into a tilt of the axis of the cutting tool corresponding to the angle of inclination of the radius, as represented by impulses required to move the axis from the reference line to the required inclination, thereby maintaining the cutting tool substantially normal to the surface to be machined and varying the inclination of the axis of the cutting tool as the surface curvature varies in order to maintain the cutting tool axis in this normal or perpendicular position.

Another object is to provide an apparatus for producing the magnetic tape according to the foregoing system wherein the drawing carrying the several views of the part or article to be machined is placed on a scanning board and scanned by photo-electric line followers mounted on carriages, the motions of which are communicated to the several channels of the tape by impulses representing the distances from their respective coordinates.

Another object is to provide an apparatus of the foregoing character wherein two photo-electric line followers are mounted on a single moving carriage but pursue independent paths as they follow corresponding moving points on their respective lines on two different views of the part to be produced, with the information representing the geometrical coordinates of these different points transferred as impulses to the different channels of the magnetic tape which is subsequently used to control the motions of a machine tool.

Another object is to provide an apparatus of the foregoing character wherein a line on a draft or loft is scanned by two photoelectric line followers in two corresponding views, the movement of each scanner is recorded by a tape recorder, and from this recorded information the apparatus will automatically draw the line in its true projection in a third view, thereby relieving the draftsman of much tedious work transferring sufficient corresponding points manually to draw the line in its arcuate projection in a third view.

Other objects and advantages of the invention will become apparent during the course of the following description of the accompanying drawings, wherein:

FIGURE 1 is a diagrammatic top plan view of a system of converting the successive positions of corresponding points in the several views of a drawing of a part or article to be produced into impulses in the several channels of a magnetic tape corresponding to the coordinate positions of the points from rectangular reference coordinates on the drawing;

FIGURE 2 is a diagrammatic view showing the position required for the photoelectric line follower in making the magnetic control tape and also the position of the end mill for cutting the corresponding surface from the magnetic tape at the position in the side elevation in FIGURE 1 as shown in the position of the lower line follower in the lower central portion thereof; and

FIGURE 3 is a diagrammic view similar to FIGURE 2 but showing the corresponding positions of line follower and end mill in the front elevation of FIGURE 1,

in the position of the line follower in the lower left-hand corner thereof.

Plotting board and carriage construction Referring to the drawings in detail, FIGURE 1 shows an apparatus, generally designated 10, for recording the lines upon a metal plate, such as sheet aluminum approximately inch thick which has previously been covered with a white coating, so as to provide the maximum contrast between the black line, which is approximately 4- or 5 thousandths of an inch wide against the white background to facilitate the operation of the optical line followers mentioned below. The alignment of the several views causes given points on any lines of the side elevation A to be immediately below the corresponding points on the corresponding lines of the top plan view A,, and immediately beside the corresponding points of the lines of the front and rear elevations A; and A The article A shown in these several views is illustrated as the drawing of an automobile body but the advantages of the invention are obviously not limited to automobile bodies but extend to any three-dimensional object which may be represented by such views. It may be necessary, however, to draw true views and sections in addition.

The scanning board 12 for reference purposes is provided with an origin 0 of three-dimensional rectangular coordinates selected according to an arbitrarily asumed arrangement, these arrangements differing with the particular company employing such layout systems. The system employed by one large automobile company locates the origin 0 for an automobile body drawing immediately below the mid-point of the front axle on the center line of the body. In the side elevation A the X-axis OX extends longitudinally of the automobile body coincident with the center line of the body, and the Z- axis OZ extends perpendicular to the X-axis OX in a direction which in the actual article would be vertical. The distances to the left of the origin 0 in the side elevation A are considered minus and distances to the right of the origin 0 along the X-axis are considered plus. Distances upward along the Z-axis from the origin 0 are considered plus. In the example chosen, there are no distances downward from the origin 0.

Considering the top plan view A in FTGURE 1, the X-axis O-X, as before extends longitudinally of the article A coincident with its center line, whereas the Y-axis extends perpendicularly thereto in a direction which would be transverse of the automobile body selected as the article A, thus coinciding with the center line of the front axle. In this particular example, the article A is assumed to be symmetrical on opposite sides of the origin in both the top plan view A and end elevations A and A hence only one half of the object A is illustrated. Thus, the X, Y and Z axes define planes which are mutually perpendicular planes including the origin 0. The relationship of the mutually perpendicular Y and Z axes relatively to the origin 0 are also shown in the front and rear end elevations A: and A in FIGURE 1.

Should occasion arise to have a different value of Y for the right-hand side than for the left-hand side, the values would be called Y for the right-hand and Y for the left-hand part.

Mounted for rectilinear guided movement above and along the scanning board 12 is a main bridge or carriage 14 which is propelled lengthwise of the scanning board 12 in the direction of the X-axis by parallel screw shafts 16 and 18 carrying bevel gears 2d and 22 meshing with corresponding bevel gears 24 and 26 on a cross shaft 28 so that the parallel screw shafts 16 and 18 will rotate in the same direction, for example, both clockwise to an observer looking from the left to the right at the lefthand end of FIGURE 1. The screw shaft 18 is also connected through reduction gearing 35 to an electric motor 32, the reduction gearing St), for example, being worm gearing, so that the screw shafts 1.6 and 18 rotate slowly in the same direction by the more rapidly rotating motor 32.

Also mounted for rectilinear guided movement above and along the scanning board 12 independently of the main bridge 14 are auxiliary bridges or carriages 34 and 36. The auxiliary bridge 34 is propelled in the direction of the X-axis along the plotting board 12 by a pair of parallel screwshafts 3t and 46) carrying bevel gears 42 and M respectively which mesh with bevel gears 4-6 and 43 on the opposite ends of a cross shaft 5%) in such a manner that the screw shafts 38 and 4t) rotate in the same direction at the same speeds. The screw shaft 33 is connected through reduction gearing 52 to an electric motor 54 in a manner similar to that described for the screwshaft 18 and motor 32. The auxiliary bridge 36 is propelled in the direction of the X-axis along the scanning board by a pair of parallel screwshafts 56 and 53 carrying bevel gears 66 and 62 respectively which mesh with bevel gears 64 and 66 on the opposite ends of a cross shaft 68 in such a manner that the screwshafts 56 and 58 rotate in the same direction at the same speeds. The screwshaft 56 is connected through reduction gearing 70 to an electric motor 72 in a manner similar to that described above.

Line-following and m0flan-transmitting arrangement Mounted on the main bridge or carriage l4 and extending from end to end thereof is a precision toothed rack 74 (FIGURE 1). The main bridge or carriage 14 serves as a guideway for an elevation cross carriage 76 and a plan cross carriage 78 operating on opposite halves of the main bridge 14 to travel back and forth therealong propelled by two screwshafts 8% and 82, each extending from the outer end of the main bridge or carriage 14 toward one another to a bearing block 81 located near the approximate midportion of the main bridge 14 but providing adequate travel of the cross carriages 76 and 78 over their respective views A and A The screwshafts and 82 are rotated independently of one another by electric speed-reducing motors 84 and 86 respectively and the cross carriages 76 and 78 are internally-threaded to be moved back and forth along their respective screwshafts 8-0 and 32 in response to the rotation thereof by the motors $4 and 86. Mounted on the elevation cross carriage 76 and plan cross carriage '78 are elevation and plan opticalelectronic line followers or contour followers 88 and 90 respectively of conventional construction including a scanning device and a sensing head. Such an optical-electronic line or contour follower with a scanning device and the necessary electrical circuit and components, for example, were described in an illustrated article by T. M. Berry entitled Optical Contour Follower in the June 1950 issue of the General Electric Review, published by the General Electric Company at Schenectady, N.Y., and further described in a pamphlet No. GEC 548 entitled GE. Contour Following System under N0. 8851, published in June 1949, November 1949 and August 1950 by the Apparatus Department of the General Electric Company, Schenectady, N.Y. Briefly described, it consists of a microscope objective and rotary Dove prism system focused on a photo-electric device. This line follower scans the line L on the drawing D and by balancing the image density on opposite sides of the line maintains a position with its center traveling directly above the line, with a self-correcting action which brings it back to the line whenever any tendency to stray from the line develops.

Also mounted on the elevation and plan cross carriages 76 and 755 are pinions 92 and 94 (FIGURE 1) meshing with the teeth of the rack 74 and mounted on the input shafts of elevation and plan synchro-transmitters )6 and 93 respectively, in such a manner that the motion of the cross carriages 76 and 73 and their particular positions at any instant on the main carriage or bridge 14 are transmitted by the synchro-transmitters 86 and 9'8 operated by their respective pinions 92 and 94 as the latter roll along the toothed rack 74-. The motion and position signals transmitted by the synchro-transmitters 96 and 98 are carried by flexible cables 1% and 102 respectively to a junction panel, generally designated 104, from which interconnection is made to other parts of the circuits, as described below.

In a similar manner, the auxiliary bridges or carriages 34 and 36 are provided with precision racks 106 and 108 and also 'guideways for optical-electronic front and rear line follower cross carriages 110 and 112 respectively carrying conventional line followers 114 and 116 respectively similar to the line followers 88 and 90 described above and similarly provided with pinions 118 and 120 meshing with the racks 106 and 188 and mounted on the input shafts of synchro-transmitters 122 and 124. These in turn are connected by flexible electric cables 126 and 128 running to the junction panel 104.

Like the cross carriages 76 and 78, the end view cross carriages 110 and 112 are propelled to and fro along their respective auxiliary bridges or carriages 34 and 36 by being internally-threaded to engage correspondinglythreaded rotary screwshafts 130 and 132 respectively. The screwshafts 130 and 132 are journalled in their re spective cross carriages 34 and 36 and rotated by speedreducing motors 134 and 136 respectively. The speedreducing motors 32, 54 and 72 which move the main carriage 14 and auxiliary carriages 34 and 36 along the plotting board 12 are connected by conductor cables 138, 148 and 142 to the junction panel 104 for their control and energization. The speed-reducing motors 84, 86, 134 and 136 for moving the cross carriages 76, 78, 110 and 112 respectively along their respective main and auxiliary carriages 14, 34 and 36 are connected by conductor cables 144, 146, 148 and 150 respectively to the junction panel 104 for their control and energization.

The motions and distances of travel of the main bridge or main carriage 14 along the scanning board 12 are measured off from the origin 0 by synchro transmitters 152 and 154 mounted on opposite ends of the main carriage 14 and having input shaft pinions 156 and 158 meshing with and rolling along the stationary racks 160 and 162 mounted parallel to the X-axis. The synchrotransmitters 152 and 154 are in turn connected by multiconductor electric cables 164 and 166 to the junction panel 104. Should both synchro-transmitters not measure the same distances from 0, thereby indicating a misof travel along the X-axis from the origin 0. The synchrotransmitters 168 and 170 are also provided with input shaft pinions 172 and 174 which mesh with and roll along stationary racks 176 and 178 mounted parallel to the 'X-axis of the scanning board 12. The synchro-transmitters 168 and 170 are connected by multi-conductor cables 180 and 182.

Connected in circuit with the junction panel 104 by the multi-conductor cable 184 is an electric power supply and control cabinet 186 which, as its name indicates, controls the electric power entering it from commercial electric power mains 188 to the remainder of the circuit. Connected to the junction panel 104 by rnulti-conductor cables 190 and 192 are a plotting board tape recorder 194 and a styling bridge tape-recorder 196 respectively, these being connected to one another by a multi-conductor cable 198 which in turn is connected to the junction panel 104 by a multi-conductor cable 200. The scanning board tape recorder 124 records upon multiple channels of a magnetic tape, the impulses corresponding to and measuring the distances traveled by the main and auxiliary bridges or carriages 14, 34 and 36 from their respective origins 0 along the X-axis, and also corresponding to and measuring the distances traveled by the line follower carriages 94, 96, 11%) and 112 in directions transverse to -the scanning board 12 in the directions from the origin O of the Y and Z axes respectively. Also connected to the junction panel 104 by a multi-conductor cable 202 is a position readout indicator 204 which indicates visually to the operator, in a manner similar to an electrical revolution counter, the instantaneous displacements, measured by impulses of the point at a particular instant on the various corresponding lines of the different views A,,, A A,, and A from the origin 0 along the X, Y and Z axes in windows 206 for the X-axis, 208 and 210 for the Y-axis and 212 for the Z-axis.

Finally, the indicator 204 is also provided with dials 214 and 216 and 218 which at any instant indicate the angles alpha, beta and gamma designating the position in angular and polar coordinates of the instantaneous perpendicular to the point on the curved line being followed by the line followers 88, 90, 114 and 116 respectively and aligned with them at the particular instant. These angles will represent the angles at which the rotary milling tool of the milling machine to be controlled by the magnetic tape will be commanded by the tape to assume relatively to the curved surface of the work being machined, as explained more fully below, so that a fiatended milling cutter will always machine the work Without digging into the work upon one side, as would be the case if its axis of rotation we're not perpendicular to a plane a tangent through the point of contact or, in other words, if the axis of rotation were not radial to the surface at the point of contact. The inclination of the radius at the point of contact would vary from point to point if the surface as a whole being machined were not spherical, but varied in curvature. Each point, however, can be considered as having a definite radius of curvature and therefore a definite radius at the point of contact at any particular instant. The point of contact of the axis of rotation of the cutter is defined by the X-YZ coordinates.

Also connected by a multi-conductor cable 220 to the junction panel 104 is a manual positioning control panel, generally designated 222, having four rows of Windows 224, 226, 228 and 230 and a fifth row of pushbuttons and manual control knobs 232. The rows of windows 224, 226, 228 and 230 reveal numbers indicating the displacement of any point on the scanning board 12 represented in steps along the X-axis, the two opposing directions along the Y-axis and along the Z-axis respectively from the origin coordinates O, as obtained when the pushbuttons and knobs 232 are operated manually to move the main and auxiliary bridges or carriages 14, 34 and 36 to any desired starting point from which automatic line following is to commence. In this manner, the operator is able 14, 34 and 36 and the line follower cross carriages 76,

78, 110 and 112 thereon and the electrical components thereof have been so chosen that each impulse represented on the magnetic tape produced by the apparatus shown in t the figure represents a given angle of rotation, for instance 18 degrees, if so selected, of the particular motor shaft or 20 such impulses or steps for each revolution of the motor shaft, which in turn represents a linear motion of of an inch on an axis. This in turn corresponds to a linear motion of half of of an inch or five tenthousandths of an inch per impulse. Thus, the system of the present invention provides two corrective steps per one-thousandth of an inch linear motion. The machine tool in which the magnetic tape produced by the present invention is mounted is preferably provided with identical drive motors to actuate its various feeding motions and each impulse on the magnetic tape produces one step, or 18 degrees, if so selected, of rotation of the machine tool drive motor which in turn through suitable ratio of gearing drives the feed shafts so as to move the cutting tool one-half of of an inch per step in the same manner as described above with respect to the production of the magnetic tape in the apparatus of FIGURE 1. In other words, 2000 impulses or steps correspond to one inch of linear travel of the various line followers and of the cutting tool of the ultimate milling machine or other machine tool controlled by the magnetic tapes produced by the apparatus 10.

In the foregoing specification, the details of construction, circuits and operation of the synchro-transmitters and receivers have been omitted because these devices are conventional and their details are well known to electrical engineers skilled in servo-systems, hence are beyond the scope of the present application. A description of the details of construction, wiring and operation of such servo devices is given, for example, in the well-known book Servomechanism Fundamentals by Lauer, Lesnigh and Matson, published by McGraw-Hill Book Co., New York, first edition, 1947, following page 26 therein.

Operation In the operation of the invention, let it be assumed that the necessary multiple-channel magnetic tapes have been installed in the tape recorders 194 and 196 and that the various line follower carriages 76, 78, 110 and 112 have been moved to their desired starting points on the lines of the "iews A A A: and A on the scanning board 12. How this is accomplished has been described immediately above, the motion along the X, Y and Z axes accomplished by operating the pushbuttons and knobs 232 of the manual positioning control panel 222. Thercupon the windows 224, 226, 228 and 230 indicate the resulting travel, measured in numerical steps or impulses of the above-named line followers and their carriages to the desired starting points on the selected line of the respective views of the drawing on the scanning board 12. seldom completed in all views by the average draftsman. Therefore, a means has been provided by arranging the circuits in such a manner that a line shown in two views can be recorded on a separate tape. For this purpose, the styling bridge tape recorder 196 was provided. From these recorded impulses a stylus, which replaces the optical follower, is drawing the line in the View in which the draftsman omitted it.

Also by a proportionate network and circuitry, all such lines are drawn which interpolate and respectively develop the surface between two given sections, thereby lightening the load on the draftsman who need only dcfine so-called master sections between design lines, moldings or so-called high-light lines of warped surfaces.

Should lines lie on top of each other or be so close to each other that the line follower has difficulty in following them, they can be spread on the scanning board on the drawing, by relocating through an input on the console the zero setting for the particular grid line controlling the line in space. After all surface development lines have been drawn, and the operator is ready to record the tape which will be controlling the milling machine, he will position three of the four electric line followers on the starting point in each view of the line to be cut into a model through the required inputs on the console. If all required line followers pick up the line and the position indicators agree, the operator then (switches to automatic operation by actuating the appropriate pushbuttons or knobs in the row 232 on the manual control panel 222, whereupon the line followers 88, 99, 114 and 116 commence to move automatically along the selected lines of their respective drawing views A A A and A,. This motion in turn causes their respective line follower carriages 76, 78, 110 and 112 and the main and auxiliary carriages 14, 34, and 36 to move in mutually perpendicular directions by the synchro-systems for controlling their respective operating motors 32, 53 and 74 for moving the main carriage 14 and the auxiliary carriages 34 and 36 along the scanning board 12 in the The drawings, drafts or lofts are very X-axis direction and the line follower operating motors 34, 36, 134 and 136 for moving the line follower carriages 76, 78, lit and 112 respectively in a transverse direction along the Y or Z-axes, as the case may be.

At the same time, two of the three line followers used traversing either the front or rear elevation views A, and A or the plan view or side elevation A or A automatically indicate the angle of the perpendicular to the point scanned at any given instant, thereby determining the angles alpha and beta which approach the angle of the end mill in the milling machine to be controlled by the magnetic tape which it must assume in order to properly machine the surface. These angles are indicated in FIGURES 5 and 6 and automatically determine the third angle gamma, all of these angles being registered on the dials 214, 216 and 213 as the operation of the apparatus lib proceeds. Meanwhile, the operation of the various synchro-transmitters 152 and 154 for the main carriage 14; 172 and 174 for the auxiliary carriages 34 and 36 respectively; 96 and 98 for the main line follower carriages 76 and 78 respectively; and 122 and 124 for the auxiliary line followers Ill) and 112 respectively, transmits the distances traveled in terms of steps which are indicated numerically in the windows 296, 208, 210 and 212 of the position readout indicator 204. At the same time, the impulses or steps are being recorded on the multi-channel magnetic tapes in the tape recorders 194 and 196 in the form of impulses corresponding to the numerical steps indicated on the position readout indicator 2%.

When one line of the drawing has been thus traced or scanned and the various coordinates of each point therealong have been registered on the magnetic tape channels in terms of impulses or steps from the starting point, the operator then repeats the foregoing operation for each line of the drawing which is intended to control the cutting operations of the ultimate machine tool to be controlled by the magnetic tape thus produced, until a complete set of instructions has been recorded on the magnetic tape. Other channels of the magnetic tape also record rotational speed of the cutting tool, type of cutter, change of length of cutter, angular relationship of the cutter to the X, Y, Z coordinate system as indicated by the angles alpha, beta and gamma mentioned above. The remaining channels of the conventional fourteenchannel magnetic tape may carry verbal instructions to the operator of the machine tool relative to positioning the work on the platform of the machine tool and related information deemed necessary. The speed of the tape being read by the machine will indicate the speed of the feeding motions in true time.

The description of the conventional drives consisting of motors, gear reductions and turning screws pushing stationary nuts has been selected to simplify the description of the apparatus. It may well be, if so desired, that instead as an alternate a stationary screw is located on each side of the plotting board and along each carriage base, held rigidly at each end. A revolving nut driven by a gear reduction and a motor would move the carriages and saddles equally well yet minimize the unavoidable windup of the long screws.

FIGURES 2 and 3 show diagrammatically the geometrical relationship which must exist in making the magnetic control tape according to the present invention and in subsequently using it to control the position of a cutting tool, such as an end mill T, at any instant at corresponding points on a given drawing line s-s and f in the side elevation A and front elevation A, respectively. It will be understood by those skilled in the optical contour follower art as referred to above in the article by T. M. Berry in the June 1950 issue of the General Electric Review, entitled Optical Contour Follower, that the photoelectric cell of each line follower 88 or 114 is mounted on the outer end of a swinging arm A pivoted at r in FIG- URES 2 and 3, whereas the optical centers of the line followers S8 and 114 respectively are located at c on the ends of the arms A in coincidence with the lines ss and ff being followed. The angle alpha in FIGURE 2 between the arm A of the line follower 88 and the Z-axis indicates the instantaneous position of the arm A on the instantaneous radius of the line s'-s in making the magnetic control tape and also indicates the corresponding instantaneous position of the axis of the rotary cutting tool, such as an end mill, in cutting a surface whose contour corresponds to the drawing line s-s. Similarly, FIGURE 3 indicates the angle beta between the arm A of the line follower 114 on the instantaneous radius of the line j and the Y axis at the same instant in the front elevation Af, which is also the corresponding position of the rotary cutting tool 1, such as an end end mill in cutting the contour of the surface whose contour at the same instantaneously corresponding point is indicated by the line ff. The remaining angle gamma is determinable when the angles alpha and beta are known.

What I claim is:

1. An apparatus for producing a multi-channel magnetic tape for controlling the feeding motions of a magnetic-tape-controlled machine tool cutter directly from aligned plan and side and end views of the article to be machined, said apparatus comprising a drawing scanning carrier having thereon a drawing containing aligned plan and side and end views of the article to be machined and also containing an origin of coordinates with rectangular reference coordinates extending therefrom longitudinal and laterally of said drawing carrier,

21 main carriage and an auxiliary carriage mounted adjacent and movable longitudinally along said drawing carrier above said plan and side views and above said end view respectively,

a first main line follower cross-carriage and an auxiliary line follower cross-carriage mounted respectively on said first main and auxiliary cross carriages for travel therealong laterally of said drawing carrier,

main line follower means and auxiliary line follower means mounted on said main cross-carriage and auxiliary cross-carriages respectively in simultaneous scanning relationship with corresponding points along corresponding lines of said views,

main and auxiliary carriage-moving motor means drivingly connected respectively to said main and auxiliary carriages to move the same longitudinally along said drawing carrier,

main and auxiliary cross-carriage moving motor means drivingly connected respectively to said main and auxiliary cross-carriages to move the same thereacross laterally of said drawing carrier,

synchro-transmitters mounted on said main and auxiliary carriages and cross-carriages in distance-transmitting relationship with said origins expressed in a predetermined number of transmitted impulses per unit length in said views, and

magnetic tape-recording means connected to said transmitters in impulse-receiving relationship there with and constructed and arranged to simultaneously record said received impulses in separate channels of the multi-channel magnetic tape of said taperecording means as corresponding variations of the magnetism therealong.

2. A magnetic tape-producing apparatus for machine tool control, according to claim 1, wherein plan and side elevational views are disposed in lateral alignment on said drawing carrier beneath said main carriage, wherein a second main line follower cross-carriage is mounted on said main carriage in laterally-spaced relationship with said first cross-carriage, and wherein said main line follower means includes first and second line followers mounted respectively on said first and second crosscarriages in simultaneous scanning relationship with corresponding points in corresponding lines of said plan and side elevational views.

3. A magnetic tape-producing apparatus for machine tool control, according to claim 2, wherein said main cross-carriage moving motor means includes first and second cross-carriage moving motors mounted on said first and second cross-carriages and driving the same back and forth along said main carriage independently of one another.

4. A magnetic tape-producing apparatus for machine tool control, according to claim 3, wherein independent synchro-transmitters' are mounted on said first and second cross-carriages and are connected in independent impulse-transmitting relationship with said tape-recording means to separate channels on the magnetic tape therein.

5. A magnetic tape-producing apparatus for machine tool control, according to claim 4, wherein separate syn chm-transmitters are mounted at opposite ends of said main carriage in independent transmitting relationship to said tape recording means for indicating departures from equality of travel of said opposite ends.

6. A magnetic tape-producing apparatus for machine tool control, according to claim 1, wherein separate synchro-transmitters are mounted at opposite ends of said main carriage in independent transmitting relationship to said tape recording means for indicating departures from equality of travel of said opposite ends.

7. A magnetic tape-producing apparatus for machine tool control, according to claim 6, wherein said main carriage moving means includes independent main carriage moving motors mounted at opposite ends of said main carriage in independent driving relationship therewith.

8. A magnetic tape-producing apparatus for machine tool control, according to claim 1, wherein visual distance-indicating means is provided for showing the electrical impulses transmitted in response to the travel of said carriages and cross-carriage.

9. A magnetic tape-producing apparatus for machine tool control, according to claim 1, wherein means is provided for recording on said tape the angles between the radius to the instantaneous curvature of the lines being scanned and said coordinates.

10. An apparatus, according to claim 1, wherein said main and auxiliary line follower means include two independent line followers arranged to follow corresponding points in corresponding lines of two corresponding views, and wherein an additional line follower on one of said carriages has been temporarily replaced by a scriber, said scriber drawing the projected line in a third view corresponding point for point to the lines in the two given views the lines of which are being followed in response to the following of said lines by said line followers.

References Cited in the file of this patent UNITED STATES PATENTS 2,971,808 Aller et a1. Feb. 14, 1961 2,996,348 Rosenberg Aug. 15, 1961 3,058,112 Bertelsen et al. Oct. 9, 1962 3,112,151 Buros Nov. 26, 1963 

1. AN APPARATUS FOR PRODUCING A MULTI-CHANNEL MAGNETIC TAPE FOR CONTROLLING THE FEEDING MOTIONS OF A MAGNETIC-TAPE-CONTROLLED MACHINE TOOL CUTTER DIRECTLY FROM ALIGNED PLAN AND SIDE AND END VIEWS OF THE ARTICLE TO BE MACHINED, SAID APPARATUS COMPRISING A DRAWING SCANNING CARRIER HAVING THEREON A DRAWING CONTAINING ALIGNED PLAN AND SIDE AND END VIEWS OF THE ARTICLE TO BE MACHINED AND ALSO CONTAINING AN ORIGIN OF COORDINATES WITH RECTANGULAR REFERENCE COORDINATES EXTENDING THEREFROM LONGITUDINAL AND LATERALLY OF SAID DRAWING CARRIER, A MAIN CARRIAGE AND AN AUXILIARLY CARRIAGE MOUNTED ADJACENT AND MOVABLE LONGITUDINALLY ALONG SAID DRAWING CARRIER ABOVE SAID PLAN AND SIDE VIEWS AND ABOVE SAID END VIEW RESPECTIVELY, A FIRST MAIN LINE FOLLOWER CROSS-CARRIAGE AND AN AUXILIARY LINE FOLLOWER CROSS-CARRIAGE MOUNTED RESPECTIVELY ON SAID FIRST MAIN AND AUXILIARY CROSS CARRIAGES FOR TRAVEL THEREALONG LATERALLY OF SAID DRAWING CARRIER, MAIN LINE FOLLOWER MEANS AND AUXILIARY LINE FOLLOWER MEANS MOUNTED ON SAID MAIN CROSS-CARRIAGE AND AUXILIARY CROSS-CARRIAGES RESPECTIVELY IN SIMULTANEOUS SCANNING RELATIONSHIP WITH CORRESPONDING POINTS ALONG CORRESPONDING LINES OF SAID VIEWS, MAIN AND AUXILIARY CARRIAGE-MOVING MOTOR MEANS DRIVINGLY CONNECTED RESPECTIVELY TO SAID MAIN AND AUXILIARY CARRIAGES TO MOVE THE SAME LONGITUDINALLY ALONG SAID DRAWING CARRIER, 